#include <iostream>

int main(int argc, char *argv[])
{
	using namespace std;
    int i,j;
	cout << "1st number:";
	cin >> i;
	cout << "2nd number:";
	cin >> j;
	int sum = 0;
	for (int m = i; m <= j; ++m){
		sum+=m;
	}
	cout << sum << endl;
    return 0;
}
